1. Field of the Invention
The present invention relates to a name service server, and more specifically, to a name service system and method rendering it possible to communicate in a communication environment using dynamic Internet protocol (IP) addresses with only the name of a communication target required for connection between a monitoring device and a remote control management system or between clients.
2. Discussion of Related Art
For connection between a conventional digital video recorder (DVR) and a remote control management system, or between client computers, a communication network such as a local area network (LAN), a public switched telephone network (PSTN), etc., and an IP address or a port number are required.
FIG. 1 is a block diagram illustrating connection of conventional DVRs and remote control management systems.
As shown in FIG. 1, a conventional system comprises a plurality of DVRs 10-1 to 10-n, a communication network connected to the DVRs, and a plurality of remote control management systems 40-1 to 40-m connected to the communication network.
In FIG. 1, the plurality of DVRs 10-1 to 10-n are installed at a remote site to monitor, collect, and store images of the site. When an event occurs, the DVRs send it through the communication network 30 to the remote control management systems 40-1 to 40-m.
The communication network 30 may be at least one of a communication network using a static IP address or a dynamic IP address such as a LAN, a wide area network (WAN), a PSTN, a public switched data network (PSDN), an asymmetric digital subscriber line (ADSL), or an integrated services digital network (ISDN), and connects the plurality of DVRs 10-1 to 10-n with the remote control management systems 40-1 to 40-m.
The remote control management systems 40-1 to 40-m perform various control functions such as connecting the DVRs 10-1 to 10-n through the communication network 30, viewing or searching for images, and detecting events.
Referring to FIG. 1, in order for the remote control management systems 40-1 to 40-m to connect to the DVRs 10-1 to 10-n at a remote site, the DVRs 10-1 to 10-n and the remote control management systems 40-1 to 40-m should use a communication network enabling themselves to connect to each other, and the remote control management systems 40-1 to 40-m should have network information such as an IP address and port number of the DVRs 10-1 to 10-n to be connected.
This is the same for the case where the DVRs 10-1 to 10-n connect to the remote control management systems 40-1 to 40-m. 
In FIG. 1, when the DVRs 10-1 to 10-n use static or public IP addresses, the IP address and port information do not change, and thus it is easy to connect thereto. However, when the DVRs 10-1 to 10-n are connected to a dynamic IP environment in which the IP address is variable, like an ADSL environment or a dynamic host configuration protocol (DHCP), the remote control management systems 40-1 to 40-m wanting connection should know the changed IP address every time the IP address has changed in order to connect the DVRs 10-1 to 10-n, and thus it is considerably difficult to make the connection.
In addition, when a client computer connected to an external communication network connects to a communication device that supports the network address translation (NAT) function, such as an IP sharer or a router, and attempts to connect to another client computer belonging to a private network, network information required for the connection cannot be obtained and thus connection is impossible.
Recently, a dynamic domain name system (DDNS) allowing a dynamic IP address to be used as a static IP address assigned to a leased line has been used. A DDNS server is informed of the IP address assigned to each computer from a specific program installed in the computer, and stores the IP address and a domain name as a pair. When a user requests connection, the DDNS server provides the IP address corresponding to the domain name so that the user need not directly cope with change of the IP address.
However, the DDNS is limited for Internet service such as the world wide web or e-mail utilized mainly by computer terminals and supports the port forwarding function, but the DDNS server does not store port information and only supports the port forwarding function for ports (well-known ports) related to Internet service provided in connection with specific programs installed in the user's computer, and router should be registered to DNS. Therefore, DDNS has the drawback that a side wanting connection has to know the port number of the communication target in a general application such as a DVR control application which is not an Internet service.
In addition, when a plurality of computers are connected to an IP sharer or router having the NAT function to form a private network, and connection is desired between a computer connected to an external communication network and a computer in the private network through a DDNS server, the side wanting connection should know the port number of the other computer.